// Playground - noun: a place where people can play

import UIKit

let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "yyyyMMddHHmmdd" // superset of OP's format

let str = dateFormatter.stringFromDate(NSDate())


var myString = "Hello this is a test."
var myDictionary = ["Hello":"Yo"]

for (originalWord, newWord) in myDictionary {
    myString = myString.stringByReplacingOccurrencesOfString(originalWord, withString:newWord, options: NSStringCompareOptions.LiteralSearch, range: nil)
}

println(myString)

